An X-ray CT apparatus is an apparatus which includes an X-ray source that x-irradiates a subject and an X-ray detector that is arranged at a position facing to the X-ray source to detect X-rays passing through the subject. Then, the X-ray source and X-ray detector is rotated around the subject to scan transmission images of the subject from multiple directions. A computer included in the X-ray CT apparatus processes the transmission images of the subject scanned from the multiple directions to generate a structure inside the subject as a tomographic image or a three-dimensional image, based on an X-ray absorption rate inside of the subject.
As the X-ray CT apparatus is for medical use, if an artifact is caused in an X-ray CT image, suitable diagnosis of a disease or its indication is disrupted. Also, when the diagnosis fails, the exposure given to the subject turns to be an unnecessary exposure. Therefore, the incidence of failures, such as an output signal of the X-ray detector becoming anomalous, needs to be reduced as much as possible to allow the X-ray CT apparatus to stably operate, and to prevent an artifact from being caused.
Japanese Patent Application Publication No. 2008-245695 discloses a technique with which, when the position of an X-ray detecting element which has failed (hereinafter referred to as a fault X-ray detecting element) is identified in an X-ray detector composed of a number of X-ray detecting elements, an X-ray CT image is generated in iteration, without using detection data obtained from the fault X-ray detecting element, to improve quality of the image.